High-Frequency Ultrasound Elasticity Imaging of Skin Using Surface Wave Model Corroborated by Tensile Test

High-frequency ultrasound-based elasticity imaging is a promising tool for non-invasive measurement of elasticity in epidermis and dermis layers. Therefore, in this study a high-frequency ultrafast ultrasound elasticity imaging technique with the surface wave model was developed to measure the in-vivo shear elasticity of skin. The estimated elasticity feature was compared with ex-vivo quasi-static tensile tests. A VEVO F2 system with an ultrasound transducer UHF57x (f
c
=40 MHz) was employed. An in-vivo rat skin was used as a model, while four different regions on the back skin were scanned. An external vibrator was used to generate vibrations at 1.5 kHz and 2 kHz. A customized ultrafast imaging sequence was acquired at a high frame rate (~8 kHz). The acquired frames were post-processed to calculate the dispersed surface wave speed (Cs), which was then fitted with the empirical surface wave model in viscoelastic materials to extract the shear modulus (G). Afterwards, skin samples were excised at each corresponding region for uniaxial quasi-static tensile tests. Shear moduli acquired from high-frequency elasticity imaging technique correlated well with those obtained from quasi-static tensile tests.